A communication unit and a method in a wireless communication network

Description

Technical Field

[0001] The present invention relates to a node and a method for use in a wireless communication network, in particular for optimizing route selection in such a network.

Background and Related Art

[0002] In the development of wireless/cellular communication networks and systems a good coverage and support of higher data rate, are desired. At the same time, the cost aspect of building and maintaining the system is of great importance and is expected to become even more so in the future. The topology of existing wireless communication systems has traditionally been characterized by the cellular architecture with the fixed radio base stations and the mobile stations as the only transmitting and receiving entities in the networks typically involved in a communication session.

[0003] One way to introduce diversity in the received signal is to exploit the spatial diversity offered when multiple antennas are used at the transmitter with the possibility of using one or more antennas at the receiver. The use of multiple antennas offers significant diversity and multiplexing gains relative to single antenna systems. Multiple-Input Multiple-Output (MIMO) wireless systems can thus improve the link reliability and the spectral efficiency relative to Single-Input Single-Output (SISO) system. In wireless systems it is generally not desired to include more than one antenna in the mobile terminals, since they should be kept as small and light as possible.

[0004] Another method that offers macro-diversity is relaying. A relaying system is a conventional radio network that is complemented with relay nodes. The relay nodes communicate wirelessly with other network elements, such as a base station, another relay and/or a user terminal. In this way, relay nodes can be used to introduce diversity in a system where one or both of the communicating units only has one antenna.

[0005] A cooperative relaying system is a relaying system where the information sent to an intended destination is conveyed through various routes and combined at the destination. Each route can consist of one or more hops utilizing the relay nodes. In addition, the destination may receive the direct signal from the source. Cooperative relaying system can be divided into numerous categories based on desired parameters.

[0006] P. A. Anghel, G. Leus, M. Kaveh, "Multi-User Space-Time Coding in Cooperative Networks," in Proc. of IEEE ICASSP, Hong-Kong, April 6-10, 2003, and P. A. Anghel, G. Leus, and M. Kaveh, "Distributed Space-Time Coding in Cooperative Networks," In Proc. of the Nordic Signal Processing Symposium, Norway, October 4 -7, 2002 discuss relaying schemes based on transmit diversity.

[0007] The coherent transmission for cooperating transmitters has been investigated for a regenerative case and with identical transmit powers in Yung-Szu Tu and Gregory Pottie, "Coherent Cooperative Transmission from Multiple Adjacent Antennas To a Distant Stationary Antenna Through AWGN Channels", in Proc. of IEEE VTC 2002, Birmingham, Alabama, USA, May 6-9, 2002.

[0008] In the literature numerous relaying schemes have been compared to a single hop system in order to a give general recommendation for the suitable scenarios for the deployment of a multi-hop system.

[0009] Y. Fan and J. S. Thompson, "On the Outage Capacity of MIMO Multihop Networks", IEEE Globecom 2005, St. Louis, USA, Nov. 2005 discloses a routing algorithm where the decision is based on instantaneous channel state information (CSI). This method has limitations since in practice obtaining the instantaneous CSI is not realistic in an FDD system type.

[0010] V. Sreng, H. Yanikomeroglu, and D.D.Falconer, "Relayer Selection Strategies in Cellular Networks With Peer-to-Peer Relaying," IEEE VTC Fall Oct.2003 discloses a routing algorithm based on the path-gain. A routing algorithm based on the path-gain is not optimal since the fast fading of radio channel is not taken into account in a proper way.

[0011] WO0039967 discloses a unified routing scheme for ad-hoc internetworking. D refers to the Dijsktra algorithm, which is an algorithm for solving the shortest path problem for selecting one path only.

[0012] EP1610503 discloses wireless ad hoc networks having a mesh technology and searching for a feasible route or path taking in account certain limitations without defining a scheduling during routing operation.

[0013] Musavian L. et al: "Closed-form Capacity Expressions of Orthogonalized Correlated MI MO Channels" IEEE Communications Letters, IEEE Service Centre, Pisca taway, NJ, US, vol. 8., no. 6, 1 June 2004. This document derives capacity expressions in new form.

[0014] Pei Liu et al.: "Cooperative Wireless Communications: A Cross-Layer Approach", IEEE Wireless Communications, IEEEE Service Centre, Piscataway, NJ, US, vol. 13, no 4.

[0015] This document discloses cooperative optimisation of wireless communications as a new paradigm.

Summary of the Invention

[0016] It is an object of the invention to improve route selection in wireless networks involving relay nodes.

[0017] In one aspect, the invention relates to a communication unit, typically a user terminal, for use in a wireless communication system in which a transmitting unit is arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, said node being characterized in that it comprises a processor arranged to perform the following steps:

identifying at least a first and a second communication path between the transmitting unit and the receiving unit, at least one of said paths involving the first or the second relay node,

calculating a first and a second capacity of at least one hop in the first and second communication path, respectively

communicating information related to the first and second capacity to at least one other communication node in the wireless network.

[0018] The invention also relates to a communication unit for use in a wireless communication system in which a transmitting unit is arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, said node being characterized in that it comprises a processor arranged to perform the following steps:

receiving information from another communication unit in the wireless communication system related to a first and a second capacity of at least one hop in a first and a second communication path between the transmitting unit and the receiving unit, respectively, and

selecting the relaying scheme based on the first and second calculated capacity.

[0019] This communication unit is typically the base station or one or more of the relay nodes.

[0020] The invention also relates to a method in a wireless communications network comprising at least one transmitting unit arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, of selecting a relay scheme for communication between the transmitting unit and the receiving unit, said method comprising the following steps:

identifying at least a first and a second communication path between the transmitting unit and the receiving unit, at least one of said paths involving the first or the second relay node,

calculating a first and a second capacity of at least one hop in the first and second communication path, respectively

selecting the relaying scheme based on the first and second calculated capacity.

[0021] The capacity should be a long-term capacity of the path, or hop. In a preferred embodiment the capacity is calculated based on second order statistics for the connection.

[0022] For example, the capacity may be calculated based on the equation

wherein

R is the code rate of STBC,

is the transmitted SINR,

n_t is the number of transmitting antenna

n_r is the number of receiving antenna

µ is the mean value and σ² is the variance of the channel in the second hop

[0023] A simplified version of this equation in which the variance σ² is ignored can also be used.

[0024] The basic idea is to switch between cooperative relaying selection diversity and relaying STBC in order to optimize the throughput of a multi-hop system. The switching threshold is based on the long term ergodic capacity (i.e second order statistics of the channel) and not on the instantaneous channel state information. The calculation of the mean capacity can be derived from the Taylor's series method, which allows accurate and easy way for estimating the capacity.

[0025] For instance relay selection diversity is more suitable than relay Alamouti under certain channel conditions hence none of the two schemes will yield an optimal system capacity under all channel conditions.

[0026] By optimizing route selection, the node and method according to the invention increase the system capacity of a multi-hop system.

[0027] The proposed method relies on long-term capacity data, such as the second order statistics of the channel and not on the instantaneous channel state information since the selection of relaying scheme is based on the long term ergodic capacity (i.e. second order statistics of the channel). As a consequence the proposed method is more robust against channel impairments.

[0028] The inventive method could also be implemented in a configuration in which mobile terminals are used as relay nodes, as long as the mobile terminals do not move at too high speed. Such a configuration is discussed, for example, in. A. Anghel, G. Leus, M. Kaveh, "Multi-User Space-Time Coding in Cooperative Networks," in Proc. of IEEE ICASSP, Hong-Kong, April 6-10, 2003 and in M. Dohler, E. Lefranc, H. Aghvami, "Space-Time Block Codes for Virtual Antenna Arrays," in Proc. of IEEE PIMRC2002, Lisbon, Portugal, September 15 - 18, 2002.

Brief Description of the Drawings

[0029] The invention will be described in more detail in the following, by way of example and with reference to the appended drawings in which:

Figure 1 is a system model showing a base station, a user terminal and two relay nodes.

Figure 2 is a flow chart of a method according to the invention.

Figures 3a and 3b illustrate the ergodic capacity in the system of Figure 1 based on simulation and on the proposed method, respectively.

Detailed Description of Embodiments

[0030] A system model including one base station 1, one user terminal 3 and two relay nodes RN1, RN2 is shown in Fig. 1. The user terminals in the system can be served by both relay nodes RN1, RN2 cooperatively or served by one of the relay nodes. It is assumed, for the sake of this example, that the first hop is perfect, and the purpose is to choose the relay node based on the second hop to maximize the ergodic capacity. The user terminal that needs relaying can be served by [RN1], [RN2], or [RN1, RN2]. It is also assumed that the total available transmit power is constant or limited.

[0031] The relay selection criterion can be determined by calculating a capacity for each possible relaying scheme and comparing the calculated capacities, as will be discussed below. Typically, the case with the highest capacity can be selected, although it may be possible to take other considerations into account. When the user terminal is near the first relay node RN1, the scheme where the entire transmit power is used by the first relay node would give the highest capacity, and therefore this relaying scheme could be chosen. When the user terminal is near the second relay node RN2, the scheme where the entire transmit power is used by the second relay node would give the highest capacity, and therefore this relaying scheme could be chosen. When the user terminal is located approximately half-way between the relaying nodes RN1, RN2, the highest capacity will typically be achieved by letting the relaying nodes RN1 and RN2 share the available power.

[0032] In the calculations below the following definitions will be used:

R is the code rate of STBC,

is the transmitted SINR,

n_t is the number of transmitting antenna

n_r is the number of receiving antenna

H is the channel matrix between the transmitter and receiver

E{·} is the expected value of its argument

[0033] According to Leila Musavian, Mischa Dohler, et al, "Closed-Form Capacity Expression of othogonalized correlated MIMO channels", IEEE communication letters, VOL.8, No. 6, June, 2004, the capacity of distributed STBC is

[0034] The channel matrix H between the transmitter and receiver is given by:

Where h_ij is the clement of the channel matrix H .

[0035] The ergodic capacity C_erg is

where f_λ^(λ) is the probability density function of ^λ, and ^λ is given by:

[0036] According to Eq. (1), the capacity C can be written as

Where

[0037] Expanding Eq. (5) by using the Taylor series of the capacity expression in the neighboring of a variable x₀ yields,

[0038] Let x₀ = µ_x,

[0039] Submitting Eqs. (7) and (9) into Eq. (11) yields,

[0040] From Eq. (12), it is easy to understand that the ergodic capacity can be predicted given the mean value µ and the variance σ² of the channel in the second hop.

[0041] Figure 2 is a flow chart of a method according to an embodiment of the invention, used to select the optimal relaying scheme in a given situation. Referring to the system shown in Figure 1 as an example only, the method comprises the steps of

S31: identifying, in the user terminal, the different possible routes from the base station to the user terminal. Using the system of Figure 1 as an example, four different routes could be identified, that is, through the first relay node RN1, through the second relay node RN2, or through both relay nodes RN1 and RN2, or directly without involving any relay node.

S32: for each of the different possible routes, calculating in the user terminal a parameter representing a long-term capacity. This may be achieved using second order statistics, for example, by calculating the ergodic capacity according to Eq. (12). Alternative equations may be used. For example, a simplified version of Eq. 12, shown as Eq. 13 may be used. In Eq. 13 the variance σ² is ignored since it might not be accurate when the SINR is high.

S33: the user terminal reports the calculated values to the relay nodes RN1, RN2 and/or to the base station.

S34: selecting in the base station or in the relay nodes, the route having the highest capacity as determined in step S32. If the selection is done in the base station, the base station communicates the decision to all the relay nodes concerned. The decision may alternatively be made by a relay node, in which case the deciding relay node must communicate the decision to all other relay nodes concerned. Yet another alternative would be to let each relay node make its own decision based on the same data received from the user terminal.

[0042] As will be obvious to the skilled person, the scheme can easily be expanded to configurations comprising more than two relay nodes. To ensure that the optimal route is selected, in such a configuration all possible routes should be identified. It may, however, be more practical to identify only some of the routes, for example, the ones most likely to give a high capacity in a given situation.

[0043] Figure 3a illustrates simulation results based on Eq. (1) above. In the simulation, the Rayleigh channel was assumed. The user terminal was deployed in different positions, and for each position 10 000 snapshots were generated, each corresponding to a channel realization. The capacity was calculated according to Eq. (1). The ergodic capacity for a channel realization is the mean value of the capacity in all of the snapshots related to this realization. The x axis represents γ₁/(γ₁+γ₂), where γ₁ is

and

= according to Eq. (4). Hence, the x axis indirectly represents the user terminal's position. When γ₁/(γ₁+γ₂) is low, the user terminal is close to the second relay node RN2 and when γ₁/(γ₁+γ₂) is high, the user terminal is close to the first relay node RN1. The curve marked with circles represents the situation when the signal is transmitted by both relay nodes RN1, RN2 in cooperation. The curve marked with squares represents the situation when the signal is transmitted only through the first relay node RN1. The curve marked with triangles represents the situation when the signal is transmitted only through the second relay node RN2.

[0044] Figure 3b illustrates the corresponding curves obtained using Eq. (12), where only the second order statistics of the channel, that is, µ_λ and

are required. As can be seen, the curves in Figures 3a and 3b are essentially the same. Hence, the approximated method according to Eq. (12) yields substantially the same result as the simulation based on Eq. (1).

Claims

1. A communication unit for use in a wireless communication network in which a transmitting unit is arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, said communication unit being characterized in that it comprises a processor arranged to perform the following steps:

identifying at least a first and a second communication path between the transmitting unit and the receiving unit, at least one of said paths involving the first and the second relay node,

calculating a first and a second capacity of at least one hop in the first and second communication path, respectively, wherein the first and second capacity are based on second order statistics for the at least one hop in the first and second communication path, respectively, wherein calculating the capacity is based on the equation

wherein

R is the code rate of STBC,

is the transmitted SINR,

n_t is the number of transmitting antenna

µ is the mean value and σ² is the variance of the channel in a hop from the first and/or second relay node,
and

communicating information related to the first and second capacity to at least one other communication node in the wireless network.

2. A communication unit according to claim 1, said communication unit being a user terminal.

3. A communication unit for use in a wireless communication system in which a transmitting unit is arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, said communication unit being characterized in that it comprises a processor arranged to perform the following steps:
receiving information from another communication unit in the wireless communication system related to a first and a second capacity of at least one hop in a first and a second communication path between the transmitting unit and the receiving unit, respectively, at least one of said paths involving the first and the second relay node, wherein the first and second capacity are based on second order statistics for the at least one hop in the first and second communication path, respectively, wherein calculating the capacity is based on the equation

wherein

R is the code rate of STBC,

S 

N is the transmitted SINR,

n_t is the number of transmitting antenna

µ is the mean value and σ² is the variance of the channel in a hop from the first and/or second relay node.
and

selecting the relaying scheme based on the first and second calculated capacity.

4. A communication unit according to claim3, said communication unit being a base station and arranged to forward information relating to the selected relaying scheme to at least one relay node in the wireless communication system.

5. A communication unit according to claim3, said communication unit being a relay node arranged between a base station and a user terminal in the wireless communication system.

6. A communication unit according to claim5, further arranged to forward information relating to the selected relaying scheme to at least one other relay node in the wireless communication system.

7. A method in a wireless communications network comprising at least one transmitting unit arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, of selecting a relay scheme for communication between the transmitting unit and the receiving unit, said method comprising the following steps:

identifying at least a first and a second communication path between the transmitting unit and the receiving unit, at least one of said paths involving the first and the second relay node,

calculating a first and a second capacity of at least one hop in the first and second communication path, respectively, wherein the first and second capacity are based on second order statistics for the at least one hop in the first and second communication path, respectively, wherein calculating the capacity based on the equation

wherein

R is the code rate of STBC,

is the transmitted SINR,

n_t is the number of transmitting antenna

µ is the mean value and σ² is the variance of the channel in a hop from the first and/or second relay node,
and

transmitting information related to the first and second capacity to at least one other communication node in the wireless network arranged to select a relaying scheme based on the information.

8. A method for a wireless communications network comprising at least one transmitting unit arranged for wireless communication with at least one receiving unit, said network further comprising at least a first and a second relay node arranged to receive a signal from the transmitting unit and forward it to the receiving unit, of selecting a relay scheme for communication between the transmitting unit and the receiving unit, said method comprising the following steps:
receiving information from another communication unit in the wireless communication system related to a first and a second capacity of at least one hop in a first and a second communication path between the transmitting unit and the receiving unit, respectively, at least one of said paths involving the first and the second relay node, wherein the first and second capacity are based on second order statistics for the at least one hop in the first and second communication path, respectively, wherein the capacity is based on the equation

wherein

R is the code rate of STBC,

is the transmitted SINR,

n_t is the number of transmitting antenna

µ is the mean value and σ² is the variance of the channel in a hop from the first and/or second relay node,
and

selecting the relaying scheme based on the first and second calculated capacity.

Ansprüche

1. Kommunikationseinheit zur Verwendung in einem drahtlosen Kommunikationsnetzwerk, in welchem eine Sendeeinheit zur drahtlosen Kommunikation mit mindestens einer Empfangseinheit angeordnet ist, wobei das Netzwerk ferner mindestens einen ersten und einen zweiten Weiterleitungsknoten umfasst, die zum Empfangen eines Signals von der Sendeeinheit und Weiterleiten desselben an die Empfangseinheit ausgelegt sind, wobei die Kommunikationseinheit dadurch gekennzeichnet ist, dass sie einen Prozessor umfasst, der zum Ausführen der folgenden Schritte ausgelegt ist:

Identifizieren mindestens eines ersten und eines zweiten Kommunikationspfads zwischen der Sendeeinheit und der Empfangseinheit, wobei mindestens einer der Pfade den ersten und den zweiten Weiterleitungsknoten umfasst,

Berechnen einer ersten und einer zweiten Kapazität mindestens eines Hops im ersten bzw. zweiten Kommunikationspfad, wobei die erste und die zweite Kapazität auf Statistiken zweiter Ordnung für den mindestens einen Hop im ersten bzw. zweiten Kommunikationspfad basieren, wobei das Berechnen der Kapazität auf der folgenden Gleichung basiert:

wobei

R die Coderate von STBC ist,

das gesendete SINR ist,

n_t die Anzahl von Sendeantennen ist,

µ der Mittelwert ist, und σ² die Varianz des Kanals in einem Hop vom ersten und/oder zweiten Weiterleitungsknoten ist,
und

Kommunizieren von Informationen in Bezug auf die erste und die zweite Kapazität an mindestens einen anderen Kommunikationsknoten im drahtlosen Netzwerk.

2. Kommunikationseinheit nach Anspruch 1, wobei die Kommunikationseinheit ein Benutzerendgerät ist.

3. Kommunikationseinheit zur Verwendung in einem drahtlosen Kommunikationssystem, in welchem eine Sendeeinheit zur drahtlosen Kommunikation mit mindestens einer Empfangseinheit angeordnet ist, wobei das Netzwerk ferner mindestens einen ersten und einen zweiten Weiterleitungsknoten umfasst, die zum Empfangen eines Signals von der Sendeeinheit und Weiterleiten desselben an die Empfangseinheit ausgelegt sind, wobei die Kommunikationseinheit dadurch gekennzeichnet ist, dass sie einen Prozessor umfasst, der zum Ausführen der folgenden Schritte ausgelegt ist:
Empfangen von Informationen von einer anderen Kommunikationseinheit im drahtlosen Kommunikationssystem in Bezug auf eine erste und eine zweite Kapazität mindestens eines Hops in einem ersten bzw. einem zweiten Kommunikationspfad zwischen der Sendeeinheit und der Empfangseinheit, wobei mindestens einer der Pfade den ersten und den zweiten Weiterleitungsknoten umfasst, wobei die erste und die zweite Kapazität auf Statistiken zweiter Ordnung für den mindestens einen Hop im ersten bzw. zweiten Kommunikationspfad basieren, wobei das Berechnen der Kapazität auf der folgenden Gleichung basiert:

wobei

R die Coderate von STBC ist,

das gesendete SINR ist,

n_t die Anzahl von Sendeantennen ist,

µ der Mittelwert ist, und σ² die Varianz des Kanals in einem Hop vom ersten und/oder zweiten Weiterleitungsknoten ist,
und

Auswählen des Weiterleitungsschemas basierend auf der ersten und der zweiten berechneten Kapazität.

4. Kommunikationseinheit nach Anspruch 3, wobei die Kommunikationseinheit eine Basisstation und zum Weiterleiten von Informationen in Bezug auf das ausgewählte Weiterleitungsschema an mindestens einen Weiterleitungsknoten im drahtlosen Kommunikationssystem ausgelegt ist.

5. Kommunikationseinheit nach Anspruch 3, wobei die Kommunikationseinheit ein Weiterleitungsknoten ist, der zwischen einer Basisstation und einem Benutzerendgerät im drahtlosen Kommunikationssystem angeordnet ist.

6. Kommunikationseinheit nach Anspruch 5, ferner ausgelegt zum Weiterleiten von Informationen in Bezug auf das ausgewählte Weiterleitungsschema an mindestens einen anderen Weiterleitungsknoten im drahtlosen Kommunikationssystem.

7. Verfahren in einem drahtlosen Kommunikationsnetzwerk, das mindestens eine Sendeeinheit umfasst, die zur drahtlosen Kommunikation mit mindestens einer Empfangseinheit ausgelegt ist, wobei das Netzwerk ferner mindestens einen ersten und einen zweiten Weiterleitungsknoten umfasst, die zum Empfangen eines Signals von der Sendeeinheit und Weiterleiten desselben an die Empfangseinheit ausgelegt sind, zum Auswählen eines Weiterleitungsschemas zur Kommunikation zwischen der Sendeeinheit und der Empfangseinheit, wobei das Verfahren die folgenden Schritte umfasst:

Identifizieren mindestens eines ersten und eines zweiten Kommunikationspfads zwischen der Sendeeinheit und der Empfangseinheit, wobei mindestens einer der Pfade den ersten und den zweiten Weiterleitungsknoten umfasst,

Berechnen einer ersten und einer zweiten Kapazität mindestens eines Hops im ersten bzw. zweiten Kommunikationspfad, wobei die erste und die zweite Kapazität auf Statistiken zweiter Ordnung für den mindestens einen Hop im ersten bzw. zweiten Kommunikationspfad basieren, wobei das Berechnen der Kapazität auf der folgenden Gleichung basiert:

wobei

R die Coderate von STBC ist,

das gesendete SINR ist,

n_t die Anzahl von Sendeantennen ist,

µ der Mittelwert ist, und σ² die Varianz des Kanals in einem Hop vom ersten und/oder zweiten Weiterleitungsknoten ist,
und

Senden von Informationen in Bezug auf die erste und die zweite Kapazität an mindestens einen anderen Kommunikationsknoten im drahtlosen Netzwerk, der zum Auswählen eines Weiterleitungsschemas basierend auf den Informationen ausgelegt ist.

8. Verfahren für ein drahtloses Kommunikationsnetzwerk, das mindestens eine Sendeeinheit umfasst, die zur drahtlosen Kommunikation mit mindestens einer Empfangseinheit ausgelegt ist, wobei das Netzwerk ferner mindestens einen ersten und einen zweiten Weiterleitungsknoten umfasst, die zum Empfangen eines Signals von der Sendeeinheit und Weiterleiten desselben an die Empfangseinheit ausgelegt sind, zum Auswählen eines Weiterleitungsschemas zur Kommunikation zwischen der Sendeeinheit und der Empfangseinheit, wobei das Verfahren die folgenden Schritte umfasst:
Empfangen von Informationen von einer anderen Kommunikationseinheit im drahtlosen Kommunikationssystem in Bezug auf eine erste und eine zweite Kapazität mindestens eines Hops in einem ersten bzw. einem zweiten Kommunikationspfad zwischen der Sendeeinheit und der Empfangseinheit, wobei mindestens einer der Pfade den ersten und den zweiten Weiterleitungsknoten umfasst, wobei die erste und die zweite Kapazität auf Statistiken zweiter Ordnung für den mindestens einen Hop im ersten bzw. zweiten Kommunikationspfad basieren, wobei die Kapazität auf der folgenden Gleichung basiert:

wobei

R die Coderate von STBC ist,

das gesendete SINR ist,

n_t die Anzahl von Sendeantennen ist,

µ der Mittelwert ist, und σ² die Varianz des Kanals in einem Hop vom ersten und/oder zweiten Weiterleitungsknoten ist,
und

Auswählen des Weiterleitungsschemas basierend auf der ersten und der zweiten berechneten Kapazität.

Revendications

1. Unité de communication destinée à être utilisée dans un réseau de communication sans fil dans lequel une unité émettrice est agencée pour une communication sans fil avec au moins une unité réceptrice, ledit réseau comprenant en outre au moins des premier et deuxième noeuds de relais agencés pour recevoir un signal en provenance de l'unité émettrice et le transférer à l'unité réceptrice, ladite unité de communication étant caractérisée en ce qu'elle comprend un processeur agencé pour effectuer les étapes suivantes :

l'identification au moins de première et deuxième voies de communication entre l'unité émettrice et l'unité réceptrice, au moins l'une desdites voies impliquant les premier et deuxième noeuds de relais,

le calcul de première et deuxième capacités d'au moins un saut respectivement dans les première et deuxième voies de communication, dans laquelle les première et deuxième capacités sont basées sur des statistiques de deuxième ordre pour l'au moins un saut respectivement dans les première et deuxième voies de communication,

dans laquelle le calcul de la capacité est basé sur l'équation :

où

R est le débit de code de STBC,

est le SINR transmis,

n_t est le nombre d'antennes émettrices,

µ est la valeur moyenne et σ² est la variance du canal dans un saut à partir des premier et/ou deuxième noeuds de relais,
et

la communication d'informations relatives aux première et deuxième capacités à au moins un autre noeud de communication dans le réseau sans fil.

2. Unité de communication selon la revendication 1, ladite unité de communication étant un terminal d'utilisateur.

3. Unité de communication destinée à être utilisée dans un système de communication sans fil dans lequel une unité émettrice est agencée pour une communication sans fil avec au moins une unité réceptrice, ledit réseau comprenant en outre au moins des premier et deuxième noeuds de relais agencés pour recevoir un signal en provenance de l'unité émettrice et le transférer à l'unité réceptrice, ladite unité de communication étant caractérisée en ce qu'elle comprend un processeur agencé pour effectuer les étapes suivantes :
la réception d'informations en provenance d'une autre unité de communication dans le système de communication sans fil relatives à des première et deuxième capacités d'au moins un saut respectivement dans des première et deuxième voies de communication entre l'unité émettrice et l'unité réceptrice, au moins l'une desdites voies impliquant les premier et deuxième noeuds de relais, dans laquelle les première et deuxième capacités sont basées sur des statistiques de deuxième ordre pour l'au moins un saut respectivement dans les première et deuxième voies de communication, dans laquelle le calcul de la capacité est basé sur l'équation :

où

R est le débit de code de STBC,

est le SINR transmis,

n_t est le nombre d'antennes émettrices,

µ est la valeur moyenne et σ² est la variance du canal dans un saut à partir des premier et/ou deuxième noeuds de relais,
et

la sélection du schéma de relais sur la base des première et deuxième capacités calculées.

4. Unité de communication selon la revendication 3, ladite unité de communication étant une station de base et agencée pour transférer des informations relatives au schéma de relais sélectionné à au moins un noeud de relais dans le système de communication sans fil.

5. Unité de communication selon la revendication 3, ladite unité de communication étant un noeud de relais agencé entre une station de base et un terminal d'utilisateur dans le système de communication sans fil.

6. Unité de communication selon la revendication 5, agencée en outre pour transférer des informations relatives au schéma de relais sélectionné à au moins un autre noeud de relais dans le système de communication sans fil.

7. Procédé dans un réseau de communication sans fil comprenant au moins une unité émettrice agencée pour une communication sans fil avec au moins une unité réceptrice, ledit réseau comprenant en outre au moins des premier et deuxième noeuds de relais agencés pour recevoir un signal en provenance de l'unité émettrice et le transférer à l'unité réceptrice, permettant la sélection d'un schéma de relais pour une communication entre l'unité émettrice et l'unité réceptrice, ledit procédé comprenant les étapes suivantes :

l'identification au moins de première et deuxième voies de communication entre l'unité émettrice et l'unité réceptrice, au moins l'une desdites voies impliquant les premier et deuxième noeuds de relais,

le calcul de première et deuxième capacités d'au moins un saut respectivement dans les première et deuxième voies de communication, dans lequel les première et deuxième capacités sont basées sur des statistiques de deuxième ordre pour l'au moins un saut respectivement dans les première et deuxième voies de communication,

dans lequel le calcul de la capacité est basé sur l'équation :

où

R est le débit de code de STBC,

est le SINR transmis,

n_t est le nombre d'antennes émettrices,

µ est la valeur moyenne et σ² est la variance du canal dans un saut à partir des premier et/ou deuxième noeuds de relais,
et

la transmission d'informations relatives aux première et deuxième capacités à au moins un autre noeud de communication dans le réseau sans fil agencé pour sélectionner un schéma de relais sur la base des informations.

8. Procédé dans un réseau de communication sans fil comprenant au moins une unité émettrice agencée pour une communication sans fil avec au moins une unité réceptrice, ledit réseau comprenant en outre au moins des premier et deuxième noeuds de relais agencés pour recevoir un signal en provenance de l'unité émettrice et le transférer à l'unité réceptrice, permettant la sélection d'un schéma de relais pour une communication entre l'unité émettrice et l'unité réceptrice, ledit procédé comprenant les étapes suivantes :

la réception d'informations en provenance d'une autre unité de communication dans le système de communication sans fil relatives à des première et deuxième capacités d'au moins un saut respectivement dans des première et deuxième voies de communication entre l'unité émettrice et l'unité réceptrice, au moins l'une desdites voies impliquant les premier et deuxième noeuds de relais, dans lequel les première et deuxième capacités sont basées sur des statistiques de deuxième ordre pour l'au moins un saut respectivement dans les première et deuxième voies de communication,

dans lequel le calcul de la capacité est basé sur l'équation :

où

R est le débit de code de STBC,

est le SINR transmis,

n_t est le nombre d'antennes émettrices,

µ est la valeur moyenne et σ² est la variance du canal dans un saut à partir des premier et/ou deuxième noeuds de relais,
et

la sélection du schéma de relais sur la base des première et deuxième capacités calculées.

Drawing